fbset: respect rgba configuration lines in fb.modes

fbset: respect rgba configuration lines in fb.modes

The fbset utility would not respect "rgba" config entries in
the fb.modes file such as this (for the ARM Integrator/CP):

mode "640x480-60-clcd"
    # D: 25.175 MHz, H: 31.469 kHz, V: 59.94 Hz
    geometry 640 480 640 480 16
    timings 39722 48 16 33 10 96 2
    rgba 5/10,5/5,5/0,1/15
endmode

This is important especially for this ARGB5551 device which
is hopeless to configure otherwise. I noticed this lacking
feature after the TI "fbtest" program managed to set up the
the colormode correctly.

Signed-off-by: Linus Walleij <triad@df.lth.se>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>